Paul T. Lynch

Plant regeneration and micropropagation of Brachypodium distachyon

Brachypodium distachyon (L.) P. Beauv. has several features of its genome and growth habit reminiscent of Arabidopsis thaliana (L.) Heyn. that may allow it to be developed as a model molecular genetic system representative of the temperate grasses. In order for B. distachyon to be exploited in this way, it will be necessary to develop tissue culture procedures. This report details initial studies of the characteristics of mature seed-derived callus and the production of fertile plants from callus of three ecotypes of B. distachyon. Optimum development of embryogenic callus occurred on LS (Linsmaier & Skoog 1965) and N6 (Chu et al. 1975) media containing 3.0% w/v sucrose and 11.25 μM (2.5 mg l-1) 2,4-dichlorophenoxyacetic acid. Plants were recovered at a high frequency from embryogenic callus of ecotype B200 maintained on growth regulator-free N6 medium and were easy to establish in compost. A method was also developed for the in vitro clonal propagation of shoots using MS (Murashige & Skoog 1962) medium supplemented with 4 to 13 μM (1.0 to 3.0 mg l-1) benzyladenine. It was concluded that B. distachyon performed well in tissue culture and was suitable for further studies aimed at genetic transformation and its continued development as a model molecular genetic system.

The use of the iron chelating agent desferrioxamine in rice cell cryopreservation: a novel approach for improving recovery

Abstract The iron chelating drug, desferrioxamine is used to suppress oxidative stress in mammalian transplant organs subjected to cold storage. The efficacy of desferrioxamine in improving post-thaw survival in cryopreserved cells from two rice culture lines was evaluated. Unfrozen rice cells maintained proliferation capacity over a fifteen day time course when exposed to concentrations of desferrioxamine > 10 mg·l −1 . Albeit, growth was reduced compared to controls. Short-term applications of the drug at concentrations of 0.5 and 10 mg·l −1 before cryopreservation and during the early post-thaw period had a positive affect on recovery as assessed by cell proliferation and triphenyl tetrazolium chloride reduction capabilities. The pharmaceutical properties of desferrioxamine are attributed to iron sequestration and the prevention of harmful Fenton and free radical chemistry. However, desferrioxamine did not significantly reduce lipid peroxidation in cryopreserved rice cells.

Effects of osmotic pretreatments on oxidative stress, antioxidant profiles and cryopreservation of olive somatic embryos

A three-day pretreatment of olive somatic embryos (SE) with 0.75 M sucrose, combined with cryoprotection (0.5M DMSO, 1M sucrose, 0.5M glycerol and 0.009 M proline) and controlled rate cooling, supported regrowth (as 34.6% fresh weight gain) and resumption of embryo development after cryopreservation. Pretreatment with mannitol or sorbitol did not support regrowth. Profiles of sugars, proline, antioxidant enzymes, Reactive oxygen species (ROS), secondary oxidation products and ethylene were constructed for the most successful (0.75 M) pretreatment series. Sucrose was the optimal pretreatment for supporting recovery, it also elevated glutathione reductase (GR) activity compared to controls, whereas superoxide dismutase (SOD), catalase and guaiacol peroxidase activities remained relatively unchanged. Superoxide dismutase activity was higher in SE pretreated with sucrose, compared with those pretreated with polyols; H(2)O(2) was enhanced in SE pretreated with sorbitol and sucrose compared to mannitol. The overall trend for ethylene and OH production revealed their levels were highest in SE pretreated with polyols albeit, for individual treatments this was not always the case. Generally, pretreatments did not significantly change embryo secondary oxidation profiles of ThioBarbituric Acid Reactive Substances (TBARS) and Schiffs bases. In combination these studies suggest oxidative processes may influence regrowth of cryopreserved olive SE and that optimal pretreatments could, in part, increase tolerance by an overall enhancement of endogenous antioxidants (particularly GR), proline and sugars.

Trace Elements in Tea ( Camellia sinensis ) and their Bioavailability

In the context used by most consumers, tea is a beverage consisting of an infusion of processed and dried tea leaves. Human exposure to trace elements from tea consumption depends upon the trace element content of commercially produced teas, the transfer of these elements into the tea infusion, and the bioavailability of the elements in the human system. The transfer of trace elements into a tea infusion can be highly variable. As tea is a source of both essential and toxic elements, the intake of tea in the human diet can be beneficial or harmful. Bioavailability studies have shown that tea can be a useful source of some essential elements in the human diet and that moderate amounts of tea consumption is unlikely to have any harmful effect on healthy individuals. However, excessive consumption of tea can result in a person exceeding the allowable elemental intake for some elements.

Effects of post-harvest storage of Allium sativum bulbs on the cryopreservation of stem-discs by encapsulation/dehydration

Summary Cryostorage of vegetatively propagated Allium species is important for the long-term conservation and sustainable use of Allium germplasm. Cryopreservation of clonally-propagated crops such as Allium is a complex, multicomponent process where both cryogenic and non-cryogenic factors can influence the outcome of storage. This study demonstrates that the duration of post-harvest storage of bulbs significantly affected the frequency of shoot regrowth following cryostorage of Allium sativum. Post-cryostorage survival of stem-disc quarters was highest (75%) following a storage period of 5 months. The highest frequency of regrowth (55%), after 4 months of storage, corresponded to an average regeneration frequency of 1.9 shoots per stem-disc quarter. These results show the importance of the physiological state of bulbs, and the need to optimise the duration of storage to break bulb dormancy, in order to improve the cryopreservation of A. sativum stem-discs using encapsulation/dehydration.

Influence of seed position within the fruit on seedling quality and in vitro shoot tip production of jackfruit

ABSTRACT This study reports on the influence of seed position within the fruit and shoot development on the production of jackfruit in vitro. Seeds were extracted from the different sections in the fruit and shoot tips excised from the resultant seedlings. The tips were cultured in vitro on media supplemented with 6-benzylaminopurine (BAP) or thidiazuron (TDZ). The seeds from the middle and basal sections of the fruit were larger and produced larger seedlings than those from the top. Seeds from the basal position took 10 days to germinate and produced seedlings 11 cm tall with four or five leaves. Partially covered and fully open shoots from 6–8 week-old seedlings performed best. The highest frequency of shoot induction (100%) and multiple shoot production (7.31 ± 1.2) with a mean length of 3.6 ± 0.13 cm was observed on Murashige and Skoog (MS) media supplemented with 3.0 mg/L BAP. Driver and Kuniyuki (DKW), and MS media were equally effective in shoot multiplication. More than 80% of the rooted plants survived culture, indicating that this technology could be used to conserve wild germplasm.